The Machangqing copper-molybdenum deposits, Yunnan, China — an example of Himalayan porphyry-hosted Cu-Mo mineralization     

Z. Peng  M. Watanabe  K. Hoshino  S. Sueoka  T. Yano  H. Nishido 《Mineralogy and Petrology》1998,63(1-2):95-117

Summary The Machangqing copper-molybdenum deposits occur in the Shanjian fold belt, Yunnan Province, China. Two types of ores are distinguished: (1) Cu-Mo quartz veinlets in magnetite-series granite porphyry; and (2) Cu-Mo skarns occurring at the contact between the Ordovician sedimentary sequence and the granite porphyry. With decreasing temperature and of hydrothermal fluids initially in equilibrium with K-feldspar, the following alteration patterns developed within the porphyry, from the center outwards: silicification, K-silicate, phyllic and argillic alteration. The paragenetic sequence of alteration minerals observed in the Cu-Mo skarns resulted from decreasing temperature and/or increasing of the hydrothermal fluids initially in equilibrium with grandite garnet. Fluid inclusions in quartz suggest boiling during the mineralization. The mineralization temperatures based on filling temperatures and salinities of quartz are in the following ranges: about 265° to 400 °C and 5.0 to 14.6 wt.% NaCl eq. for the Cu-Mo veinlets; and 200° to 500 °C and 10.2 to 42.0 wt.% NaCl eq. for the Cu-Mo skarns. As is evident from log fo₂-pH diagrams, ores of the early stage of mineralization in the Cu-Mo skarns, characterized by the assemblage magnetite + pyrite + rare pyrrhotite + K-feldspar + quartz, were deposited from highly alkaline and high temperature fluids. With decreasing temperature and fo₂, the pH of the ore fluids was shifted towards slightly alkaline to neutral, with the resultant formation of the main stage ores, characterized by the assemblage chalcopyrite + pyrite + molybdenite + sphalerite + K-feldspar +sericite (muscovite) + epidote + uartz. Very minor amounts of ore minerals, including matildite, bismuthinite and electrum, are associated with a late stage of ore formation.In the case of the Cu-Mo veinlets, it can be stated roughly that both fs₂ and fo₂ conditions were in the stability field of pyrite, with pH of the ore fluids buffered by the assemblage sericite + K-feldspar +quartz ± calcite. K-Ar age determinations were made on the granite porphyry, biotite phenocrysts and hydrothermal biotite in the Cu-Mo skarns, giving ages of 42.5 to 34.6 Ma, 52.3 Ma, and 39.2 to 26.4 Ma, respectively.It is concluded that the Cu-Mo mineralization at Machangqing shows a close spatial and temporal association with the Himalayan felsic magmatism of the magnetite-series type.

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Die Machangqing Kupfer-Molybdän-Lagerstätten, Yunnan, China — Ein Beispiel für prophyrische Cu-Mo Vererzung im Himalaya

Zusammenfassung Die Kupfer-Molybdän-Lagerstätten von Machangqing treten im Shanjian Faltengürtel in der Provinz Yunnan, China, auf. Zwei Erztypen sind unterscheidbar: (1) Cu-Mo Quarzgängchen in einem porphyrischen Granit der Magnetit-Serie; (2) Cu-Mo-Skarne am Kontakt zwischen der ordovizischen Sedimentabfolge und dem porphyrischen Granit. Mit Abnahme der Temperatur und des Verhältnisses der hydrothermalen Fluide, die ursprünglich mit Alkalifeldspat im Gleichgewicht waren, entwickelten sich in diesem Porphyrstock vom Zentrum randwärts folgende Alterationszonen: Silizifizierung, K-silikatische, phyllische und argillische Alteration. Die paragenetische Abfolge der Alterationsminerale, die in den Cu-Mo Skamen zu beobachten sind, sind das Resultat abnehmender Temperatur und/oder einer Zunahme des -Verhältnisses der hydrothermalen Fluide, die ursprünglich mit Grandit-Granat im Gleichgewicht waren. Flüssigkeitseinschlüsse in Quarz weisen auf Siedeprozesse während der Mineralisation hin. Die aus den Einschlußtemperaturen und Salinitäten in Quarz bestimmten Mineralisationstemperaturen liegen für die Cu-Mo-Gängchen zwischen 265–400 °C und zwischen 5–14.6 Gew.% NaCI Äquiv. und zwischen 200–500 °C und 10.2–42 Gew.% NaCI Äquiv. für die Cu-Mo Skarne. Wie aus log fo₂-pH Diagrammen hervorgeht, ist die im Frühstadium der Cu-Mo Skamvererzung entstandene Vergesellschaftung von Magnetit +Pyrit+selten Magnetkies + Alkalifeldspat + Quarz durch Ausfällung aus sehr alkalischen und hochtemperierten Fluiden entstanden. Mit Temperatur- und fo₂-Abnahme wurde der pH der Lösungen leicht alkalisch bis neutral. Dies resultierte in der Bildung der Erze des Hauptstadiums, das durch Chalcopyrit + Pyrit + Molybdänit + Sphalerit + Alkalifeldspat + Serizit (Muscovit) + Epidot + Quarz charakterisiert ist. Sehr geringe Mengen an Erzmineralen inklusive Matildit, Bismuthinit und Elektrum sind dem Spätstadium der Vererzung zuzuordnen. Für die Cu-Mo-Gängchen läßt sich etwas verallgemeinernd feststellen, daß fo₂ und fs₂ im Stabilitätsbereich von Pyrit lagen, wobei der pH der Erzfluide durch die Paragenese Serizit+Alkalifeldspat+Quarz+Calcit gepuffert wurde. K-Ar Altersbestimmungen wurden am porphyrischen Granit, an Biotit-Phänokristallen und an hydrothermal gebildetem Biotit der Cu-Mo Skarne durchgeführt. Sie ergaben Alter von 42.5–34.6, 52.3 bzw. 39.2-26.4 Ma.Die Cu-Mo Vererzung von Machangqing zeigt eine räumliche und zeitliche Assoziation mit dem sauren Magmatismus der Magnetit-Serie im Himalaya.

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With 12 Figures  相似文献   

Seasonal change in CO2 and H2O exchange between grassland and atmosphere     

N. Saigusa  S. Liu  T. Oikawa  T. Watanabe 《Annales Geophysicae》1996,14(3):342-350

The seasonal change in CO₂ flux over an artificial grassland was analyzed from the ecological and meteorological point of view. This grassland contains C₃ and C₄ plants; the three dominant species belonging to the Gramineae; Festuca elatior (C₃) dominated in early spring, and Imperata cylindrica (C₄) and Andropogon virginicus (C₄) grew during early summer and became dominant in mid-summer. CO₂ flux was measured by the gradient method, and the routinely observed data for the surface-heat budget were used to analyze the CO₂ and H₂O exchange between the grassland and atmosphere. From August to October in 1993, CO₂ flux was reduced to around half under the same solar-radiation conditions, while H₂O flux decreased 20% during the same period. The monthly values of water use efficiency, i.e., ratio of CO₂ flux to H₂O flux decreased from 5.8 to 3.3 mg CO₂/g H₂O from August to October, the Bowen ratio increased from 0.20 to 0.30, and the ratio of the bulk latent heat transfer coefficient C_E to the sensible heat transfer coefficient C_H was maintained around 0.40-0.50. The increase in the Bowen ratio was explained by the decrease in air temperature from 22.3 °C in August to 16.6 °C in October without considering biological effects such as stomatal closure on the individual leaves. The nearly constant C_E/C_H ratios suggested that the contribution ratio of canopy resistance to aerodynamic resistance did not change markedly, although the meteorological conditions changed seasonally. The decrease in the water use efficiency, however, suggested that the photosynthetic rate decreased for individual leaves from August to October under the same radiation conditions. Diurnal variations of CO₂ exchange were simulated by the multi-layer canopy model taking into account the differences in the stomatal conductance and photosynthetic pathway between C₃ and C₄ plants. The results suggested that C₄ plants played a major role in the CO₂ exchange in August, the contribution of C₄ plants decreased in September, and daily variations of CO₂ exchange were mainly due to C₃ plants in October. The results also suggested that the decrease in the net canopy CO₂ exchange from August to October was induced partly by the decrease of net photosynthesis on the individual leaves in both C₄ and C₃ plants, which could be due to aging of the leaves.  相似文献   

Geochemical behaviour of iron and manganese ions in the Ningyo-Toge uranium deposit district, southwest Japan     

Koji Watanabe 《Chemical Geology》1987,60(1-4):299-307

The Ningyo-Toge uranium deposit is one of the typical sedimentary uranium deposits in Japan. In general, during weathering, U is removed from the basal granite through underground water. The underground water in this area is rich in U, and has a comparatively high concentration of Fe and Mn.

In this area, three types of Fe minerals can be recognized in different modes of occurrence: (1) in the oxide zone brownish Fe-hydroxide mineral with ferric ion, i.e. goethite (-FeOOH); (2) in the reduced zone of the mine gallery pale-blue Fe-hydroxide mineral with some ferrous ion, i.e. lepidocrocite (γ-FeOOH); and (3) Fe-sulphate minerals such as melanterite (FeSO₄·7H₂O), etc. Some uranyl sulphate minerals, uranopilite and zippeite, are closely associated with these Fe-sulphate minerals. Under weakly alkaline conditions of the oxidizing environment, Mn-hydroxide (MnOOH) coexists with goethite as alternative thin laminae with shale, or coprecipitates resembling a marine Mn nodule, in the size of 0.5 cm in diameter. Radioactive anomalies have been recognized frequently for these Mn sediments due to absorption of Ra by the sediments.  相似文献   

Fine-grained aggregates in L3 chondrites     

Seiko Watanabe  Masao Kitamura  Nobuo Morimoto 《Earth and Planetary Science Letters》1987,86(2-4)

The textures and chemical compositions of the constituent minerals of the fine-grained aggregates (FGA's) of L3 chondrites were studied by the backscattered electron image technique, electron probe microanalysis, and transmission electron microscopy. Plagioclase and glass in the interstices between fine grains of olivine and pyroxene indicate that the FGA's once partly melted. Compositional zoning and decomposition texture of pyroxenes are similar to those observed in chondrules, indicating a common cooling history of the FGA's and chondrules. Therefore, the mechanism that caused melting of the FGA's is considered to be the same as for chondrules. Bulk compositions of the FGA's are within the range of those of chondrules, so some chondrules probably were produced by complete melting of the same precursor materials as those of the FGA's. The precursor materials must have included fine olivine and other grains that probably are condensates.  相似文献   

Interpretation of the soft X-ray spectra from Hinotori     

K. Tanaka  N. Nitta  K. Akita  T. Watanabe 《Solar physics》1983,86(1-2):91-100

We present analyses of the soft X-ray iron line spectra of flares obtained from the Bragg Spectrometer on Hinotori. We first present a case of strong K emission at the impulsive phase of the hard X-ray burst, and assess net K emission due to the electron impact by eliminating the fluorescence contribution. Second we discuss on the differences in the electron temperatures and emission measures derived respectively from FeXXVI and FeXXV spectra. A pilot two-temperatures model which can explain the two spectra is presented. Finally, we compare the temporal relations between the soft X-ray and hard X-ray intensities and show two extreme classes of flares, one characterized by the efficient formation of a hot thermal plasma above 30 million degree, and the other characterized by the spiky hard X-ray component. Energetical relation of the thermal plasma to the electron beam is discussed for the two classes.  相似文献   

Direct measurement of conjugate photoelectrons and predawn 630 nm airglow     

G.G. Shepherd  J.F. Pieau  T. Ogawa  T. Tohmatsu  K. Oyama  Y. Watanabe 《Planetary and Space Science》1978,26(3):211-217

A sounding rocket was flown during the predawn on 17 January, 1976 from Uchinoura, Japan, to measure directly the behaviour of the conjugate photoelectrons at magnetically low latitudes. On board the rocket were an electron energy analyzer, 630 nm airglow photometer, and plasma probes to measure electron density and temperature. The incoming flux of the photoelectrons was measured in the altitude range between 210 and 340 km. The differential flux at the top of the atmosphere was determined to be $\text{F = (1.3 ± 0.4) × 10}{}^{11}\text{exp}\text{[?}\text{E(}\text{eV}\text{)}\text{12}\text{]}$ electron · m^?2 · sr^?1 · s^?1 in the energy range 10 ? E ? 50 eV. The emission rate of the 630 nm airglow was observed in the altitude range between 90 and 360 km. The apparent emission rate observed at 80 km was 32 ± 5 R. From a theoretical calculation of the optical excitation rate using the observed electron flux data along with a model distribution of atomic oxygen, it was estimated that more than 65% of the emission could be produced by direct impact of the photoelectrons with atomic oxygen in the thermosphere between 200 and 360 km. Using the observed electron density and the model distribution of oxygen molecules the residual of the emission was ascribed to the excitation of O(¹D) through dissociative recombination, $\text{O}{}_2{}^{\mathrm{+}}\text{+}\text{e}\text{→}\text{O}{}^1\text{+}\text{O}{}^7$. The direct collisional excitation by ambient electrons is estimated to be negligibly small at the level of observed electron temperature.  相似文献   

区域最小人均耕地面积与耕地资源调控   总被引：199，自引：7，他引：199  

蔡运龙  傅泽强  戴尔阜 《地理学报》2002,12(2):127-134

耕地资源对农业和国民经济可持续发展起着不可替代的基础性作用。中国人均耕地资源短缺，快速工业化、城市化进程对耕地的占用使耕地资源更趋紧张。目前的市场机制必然驱动耕地资源不断向获利更多的用途转移，最终会危急食物安全。因此，创新耕地资源利用与保护的调控机制已迫切之至。基于中国耕地资源流失原因及态势的分析，提出了最小人均耕地面积和耕地压力指数概念，并以此为基础提出了构建耕地资源利用和管理调控机制的思路。实际数据分析结果表明，以最小人均耕地面积和耕地压力指数作为耕地保护的基本标准，能因地制宜地兼顾食物安全和经济发展对土地的需求，具有显著的科学性和可操作性。  相似文献   

Periodic activity of Comet Bradfield 1987s     

Jun-Ichi Watanabe  Takumi Abe 《Earth, Moon, and Planets》1989,44(2):141-147

A periodic brightness variation of about 6 days was found by applying maximum entropy method to the visual brightness of Comet Bradfield 1987s. This activity was clearly apparent in January of 1988. No other outstanding period was detected. This suggests that the period of the rotation or precession of the nucleus is about 6 days.  相似文献   

Plasma motions in the flare of 1982 June 6 (X12)     

Tetsuya Watanabe 《Solar physics》1990,126(2):351-366

This paper analyzes soft X-ray spectra obtained from the Hinotori spacecraft for the investigation of plasma motions during the initial phase of the great flare, 1982 June 6. The wavelength calibration of the scanning spectrometers is determined from information on the spacecraft attitude and from the position of the Fexxv resonance line during the decay phase. Hard X-ray bursts, nonthermal line broadenings and blueshifted components in X-ray lines are temporally correlated with time differences of 0–30 s. The possible contribution of the blueshifted component to the line width decreases more rapidly than the nonthermal broadening, which suggests dominant plasma motions are taking place at higher and higher altitude in the corona, because of the increase of electron density in flaring loops. The evolution of the input kinetic energy content to the thermal plasma inferred from line broadenings in the impulsive phase resembles that of the thermal energy content in the source of the Fexxvi emission, which is different from that deduced for Fexxv source. This suggests that the origins of the nonthermal line broadening and Fexxvi source are closely coupled.  相似文献   

Acoustic Doppler current profiler surveys along the Yangtze River     

Zhongyuan Chen  Dechao Chen  Kaiqin Xu  Yiwen Zhao  Taoyuan Wei  Jing Chen  Luqian Li  Masataka Watanabe 《Geomorphology》2007,85(3-4):155

An acoustic Doppler current profiler is used to characterize the river velocity against the morphology of the Yangtze River from Chonqing to the sea. High flow velocities occur in the Three Gorges section and lower velocities in the middle and lower reaches of the river. This is largely due to the change in river pattern from a high gradient deeply-cut valley to a flat fluvial plain. Flow velocities fluctuate in the middle Yangtze due to the presence of meander bends of different length. There are numerous smaller velocity fluctuations in the lower Yangtze channel that reflect multichannel pattern with numerous sand bars and a river morphology affected by bedrock outcrops. Water depths of 40–100 m occur in the Three Gorges valley but decrease to 15–40 m in the middle and lower Yangtze. At the Gezhou Reservoir, 30 km downstream of the Three Gorges damsite velocity drops to low (< 1.0 m s^− 1) 20 km reach. A second low velocity (< 0.5 m s^− 1) zone, about 20 km in length, is located in the lower Yangtze near the coast probably due to the tidal influence. The results from this research will serve as a datum for evaluating changes to the river once the Three Gorges dam is completed in 2009.  相似文献